Turbulent thermalization process in heavy-ion collisions at ultrarelativistic energies

TLDR

The study aims to distinguish between different kinetic scenarios in the classical regime of heavy‑ion collisions. The authors simulate the nonequilibrium evolution of heavy‑ion collisions at weak coupling and very high energy using lattice simulations of the classical Yang–Mills equations. Large classical‑statistical simulations reveal that the longitudinally expanding plasma’s dynamics become independent of initial conditions, evolve through a transient dominated by plasma instabilities and free streaming, and ultimately reach a nonthermal fixed point exhibiting self‑similar wave‑turbulence dynamics consistent with the bottom‑up thermalization scenario. Reference: Lett.

Abstract

The nonequilibrium evolution of heavy-ion collisions is studied in the limit of weak coupling at very high energy employing lattice simulations of the classical Yang-Mills equations. Performing the largest classical-statistical simulations to date, we find that the dynamics of the longitudinally expanding plasma becomes independent of the details of the initial conditions. After a transient regime dominated by plasma instabilities and free streaming, the subsequent space-time evolution is governed by a nonthermal fixed point, where the system exhibits the self-similar dynamics characteristic of wave turbulence. This allows us to distinguish between different kinetic scenarios in the classical regime. Within the accuracy of our simulations, the scaling behavior found is consistent with the ``bottom-up'' thermalization scenario [R. Baier, A. H. Mueller, D. Schiff, and D. T. Son, Phys. Lett. B 502, 51 (2001)].